Being stable organic materials which can be used for industrial production, plastics have been applied for various purposes.
In particular, among plastics, a so-called “engineering plastic” has excellent mechanical strength and heat resistance and can replace metallic materials, unlike general plastics such as polyethylene or polystyrene. In recent years, engineering plastic has been put into practice in various industrial contexts as an excellent functional material. Among engineering plastics, those such as polyamide, polyethylene terephthalate, polycarbonate, polyacetal, and polyphenylene ether are called “general engineering plastics”, and can provide reasonable performance and inexpensive price, and, accordingly, large amount of general engineering plastics are used in industry.
Other than general engineering plastics, plastics having extremely excellent mechanical strength and heat resistance are called “special engineering plastics or super engineering plastics”, and application thereof is limited from the standpoint of the cost or formability thereof.
Examples of special engineering plastics include polyimides, polysulfones, all-aromatic polyesters, crystalline polyesters, polyketones, cyanates, and polyphenylenesulfides.
Among engineering plastics, polyketone is a polymer having a ketone group in the main chain thereof. Main examples of polyketone include polyether ketone (hereinafter, PEK), polyether ether ketone (hereinafter, PEEK), and polyether ketone ketone (hereinafter, PEKK), and polyallyl ether ketone and aliphatic polyketone as composites thereof.
Polyallyl ether ketone is a heat-resistant polymer to which injection molding can be applied. The ratio of rigid ketone groups to flexible ether bonds is a factor for determining heat resistance of the polymer. Further, PEK or PEEK having a high proportion of ketone groups has high heat resistance, the thermal deformation temperature of PEK or PEEK ranges from about 300° C. to about 350° C., the continuous duty temperature thereof ranges from 200° C. to 260° C., and among thermoplastics, PEK or PEEK exhibits most excellent heat resistance. PEEK has a melting point of 334° C., and exhibits high resistance to hydrolysis, high chemical resistance, high radiation resistance, and incombustibility and, accordingly, is used for airplanes, atomic power generation, electronics such as computers, cable-coating materials, connectors, engine peripheral parts for automobiles, and hot water pump housings. PEK can exhibit higher heat resistance, chemical resistance, incombustibility, and radiation resistance than PEEK, and is used for atomic power generation and airplane-associated parts.
However, since these PEK and PEEK are made from expensive monomers serving as raw materials, there is little room for cost reduction, and thus it is expected that large-scale market production thereof might be difficult even in the future.
Condensed engineering plastic containing an aromatic ring in the main chain thereof has conventionally been synthesized due to a condensation reaction between two functional groups. However, in recent years, new synthesizing methods in which large ring compounds are ring-opening polymerized or they are directly polymerized by dehydrogenation have been frequently reported.
On the other hand, attention has been drawn to polyketone which does not contain an aromatic ring in its molecule or so-called aliphatic polyketones. Aliphatic polyketone (product name “Caliron”) which is developed and manufactured by Shell Oil Co., Ltd. is a special engineering plastic. Since the aliphatic polyketone does not contain an aromatic ring in its molecule and can be manufactured from inexpensive raw materials, olefin such as ethylene, and CO, a wide range of applications can be expected. Examples of applications of the aliphatic polyketone include: packaging, containers, electric members, electronic components, automobile members, building materials, gears, slide characteristic parts, adhesives, and fibers, and in these industrial fields, aliphatic polyketone is receiving much attention.
At present, aliphatic polyketone is mainly synthesized by a method in which olefin such as ethylene or propylene and carbon monoxide are copolymerized in the presence of a catalyst such as a metal complex, for example palladium, nickel or cobalt (see U.S. Pat. No. 4,835,250, for example). However, at present, the synthesis of these metal complexes is very difficult. For instance, C. Bianchini, et. al., Macromolecules 32, pp. 4183-4193 (1999) discloses a synthesis method of a palladium complex.
However, since a petroleum raw material is used in the above synthesis, there is a need to undergo a complicated reaction process including 5 steps or more, which increases the manufacturing cost.
Among aliphatic polyketones, synthesis of a polyether ketone polymer such as aliphatic polyether ketone or polyether ether ketone has not yet been reported.
Accordingly, there is a need for a method of preparing an aliphatic polymer having a ketone group in the main chain thereof, which can be used for a material such as engineering plastic, from a raw material which is easy to handle, and a method of preparing a composition using the same.